[model:bugtype] Fix the name for the performance impact field

[suhaibmujahid]

The bug_to_types function in models/bugtype.py might require an update to align with the field rename.

bugbug/bugbug/models/bugtype.py

Lines 69 to 72 in d220467

	if "cf_performance" in bug and bug["cf_performance"] not in ("---", "?"):
	types.add("performance")

Originally posted by @PromiseFru in #3895 (comment)

The field name should be cf_performance_impact instead of cf_performance.